Does anyone know the required resolution for a photograph to be used on a billboard? Would the Canon 7D be able to provide a large enough file size to meet the requirements?
Resolution becomes less of an issue the farther the viewer is from the image. As billboards are meant to be viewed from quite some distance, they are usually printed at a relatively low resolution - sometimes as low as 9dpi!
It really depends on how detailed and complex the photo is, but I'm sure the 18 megapixels provided by the 7D will provide more than enough resolution for just about any billboard.